load_textdomain tries to load the current working directory as a file

[tofandel]

It all stems from this line in wp-includes/l10n.php

<?php
                $success = $i18n_controller->load_file( $file, $domain, $locale );

                if ( $success ) {
                        if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof MO) {
                                $i18n_controller->load_file( $l10n[ $domain ]->get_filename(), $domain, $locale );
                        }

There is no guarantee that $l10n[ $domain ]->get_filename() is not empty there

And if it is, there is no sane check and it tries to load a translation on realpath('') which is the current working directory

While it doesn't cause any direct issues, this is just something I came accross while debugging and I think the following patch should be done

--- wp/wp-includes/l10n.php.old 2025-03-25 03:13:47.957506010 +0100
+++ wp/wp-includes/l10n.php 2025-03-25 03:14:15.295131388 +0100
@@ -844,7 +844,7 @@

$success = $i18n_controller->load_file( $file, $domain, $locale );

if ( $success ) {

• if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof MO ) {

+ if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof MO && !empty($l10n[ $domain ]->get_filename())) {

$i18n_controller->load_file( $l10n[ $domain ]->get_filename(), $domain, $locale );

}

Or alternatively before realpath check if $translation_file is empty in WP_Translation_Controller

Sane checking in WP_Translation_Controller::load_file, if trying to load an empty filename, abort early

Trac ticket: https://core.trac.wordpress.org/ticket/63159#ticket